What are some limitations of using Collaborative Deep learning for Recommender systems?
A good recommender program is one of the hardest problems in AI. 
Recomender needs to first know me (by talking to me or by analyzing the movies that I graded as good).
Then it needs to be able to recognize similarity of my taste to a new movie. So it needs to watch movies that I liked, build a list of common things between these movies and then watch 100 random new movies and pick the one that has the most patterns in common with my liked movies.

So once again a good similarity recognition system is the key to successfull AI.